Alternator discharging

[ddpsnake]

Good day all, my 71 has a 65 amp ALT with the 2 wire.we went for a drive last night. once it got dark and i turned on my lights all is fine until i get stop at a light all lights dim the alternator starts to discharge and the car stalls, bummer.the idle is set at 800 rpm in D.what is causing this every thing is 3 years old. thanks for your help.I dont want to be afraid of the dark lol.

 

[twecomm]

Could bad diode(s) in the alternator. Could be a bad battery.

 

[ddpsnake]

Could bad diode(s) in the alternator. Could be a bad battery.

one thing i notice there is a lot of black dust on the front of the alt

 

[Nacho-RT74]

Alternator doesn't discharge, battery does. What your alternator is not doing is holding the load required by the car to keep the battery still charged AND the car still working.

BUT if the engine stalls it means you have a fail into the alt/batt paths. Because still with a damaged alternator, the batt should be able to keep the engine spinning still being discharged untill batt dies.

 

[musekmkr]

Throw a volt meter on the battery and see what you are getting when it's running. A fully charged battery should read ~12.7 volts with engine off and ~14.7 while charging. As for the black stuff, probably unlikely but make sure your belt is not loose and at this point shot. That's what comes to mind when you say black stuff.

 

[ddpsnake]

Alternator doesn't discharge, battery does. What your alternator is not doing is holding the load required by the car to keep the battery still charged AND the car still working.

BUT if the engine stalls it means you have a fail into the alt/batt paths. Because still with a damaged alternator, the batt should be able to keep the engine spinning still being discharged untill batt dies.

well i have notice it does not spin over like it used to, bad bat, also after sitting for a week the needle on the amp gauge goes half way for a bit then goes to the middle.

 

[ddpsnake]

Throw a volt meter on the battery and see what you are getting when it's running. A fully charged battery should read ~12.7 volts with engine off and ~14.7 while charging. As for the black stuff, probably unlikely but make sure your belt is not loose and at this point shot. That's what comes to mind when you say black stuff.

just went out and check it with the engine off its 12.3.

 

[ddpsnake]

just went out and check it with the engine off its 12.3.

with engine on 15.8

 

[Nacho-RT74]

voltage can go throught a hair even rusted, amperage needs a good quality and thick path and thats what your ammeter is saying. A batt is charged with amperes on a voltage rate, but still with amperes. You have a problem on the charging path between alt and batt, mostly sure at bulkhead... burnt, melted... and even maybe loosen, rusty, dirty ammeter studs. As mentioned, even with a damaged alternator, the batt must hold the engine spining. There is no a reason to stall the engine while batt is still there.

 

[Nacho-RT74]

try to imagine this... two guys pushing a car. Voltage is the force every guy applies, amperes is the quantity of guys, resistance is the car weight along with some other factors like the road. Two guys applying same force will push better a car than one... The car demands some force to be pushed, so will demand more guys to push it. When getting closer to a hill, will demand more guys to be pushed.

BUT if the road is in bad conditions, won't be a way to push the car still applying the same force.

 

[ddpsnake]

why the dim lights i am lost on this, the hole thing.

 

[Nacho-RT74]

you are not getting amperage, and mostly sure also loosing voltage trying to keep the car and acc up... as mentioned, check the charging path between alt and batt...bulkhead, ammeter studs

 

[ddpsnake]

you are not getting amperage, and mostly sure also loosing voltage trying to keep the car and acc up... as mentioned, check the charging path between alt and batt...bulkhead, ammeter studs

View attachment 1155969

ok got it, thanks for the help big time,its like 100 degrees in my garage lol will check what you said once it cools down.

 

[ddpsnake]

ok just went out and check the bulk head connection was a little loose, push it in till it click, all is clean, pulled the red wire from bat to relay found at the end that should be red is back,the winding not good.could this be the problim

 

[gary h]

with engine on 15.8

That seems High to me.

 

[Jerry Hall]

That seems High to me.

Voltage regulator should not let it go to 15.8. As stated above 14.7, 15.0 max.

 

[ddpsnake]

Voltage regulator should not let it go to 15.8. As stated above 14.7, 15.0 max.

regulator change time?

 

[Jerry Hall]

regulator change time?

Not sure that's your entire problem, but a good start.

 

[RJRENTON]

IMO...
A functioning alternator either charges (puts out a voltage and current) or puts out nothing (no voltage or current) but alternators do not discharge (consume) power UNLESS a diode is shorted, then the alternator will consume power and discharge the battery, thru its internal resistance to ground, when the engine is off and all external loads are off.
IF the alternator has low output voltage or currrnt, then the problem lies either within the unit (open diode, bad stator windings, bad brushes or defective rotor). OR....External wiring issues (bulkhead connections) can contribute to low output current (indicated by the ammeter), but are usually manifested by melted connections at the termination point.
BOB RENTON